Large-scale data centers typically house hundreds or thousands of computer systems in high-density configurations (side-by-side racks, with multiple computing nodes per rack) in an above-ground building. Some sources estimate that up to 50% of the electrical power consumption for data centers is dedicated to cooling the environment in which the computer systems operate.
The heat generated by the internal electronic components of computing devices has long been a significant factor determining the overall system design of computer systems. The most common forms of heat dissipation in early personal computer designs were direct physical contact between the heat-generating integrated circuit chip and a heat-conducting mass such as aluminum, and non-turbulent airflow, typically generated by electrical fans, to circulate cool air through a space interior to the computer system housing. In the early large-scale computing systems of the 1940s and 1950s, heat dissipation consisted primarily of ventilation apertures in housings, followed by ambient-air fans and blowers which cooled by forced air convection.
Zelina, in U.S. Pat. No. 3,566,958 (1971), describes a means of thermally coupling heat conductors to integrated circuit chips, though without addressing how to transport the heat contained in the heat-conducting material away from the space surrounding the electrical device. In U.S. Pat. No. 3,648,113 (1972) Rathjen describes a means of stacking planar electronic devices, with spacing between the flat planes, and cooling the entire assembly using fluid flow across the flat surfaces; the cooling fluid exits the entire assembly, thereby transporting heat away from the heat-generating electronics. Austin, in U.S. Pat. No. 3,737,728 (1973) discloses a mounting structure for fragile heat-generating devices (e.g. devices used in computer apparatuses), as well as uniformity of heat conduction and good heat dissipation away from the core assembly area. These ideas are combined in U.S. Pat. No. 3,865,183 (1975), in which Roush describes a more comprehensive means of constructing a full computer assembly with good heat dissipation characteristics of the individual circuit boards in the module, with fluid flow for removal of heat energy from the assembly.
As semiconductor densities in computing devices continued to increase, progressively more heat was generated by the devices. Beginning in the 1980s a series of advancements was made in the heat removal capabilities of computer systems, primarily through the use of liquids. Oktay, in 1980 (U.S. Pat. No. 4,203,129) described the bonding of a heat sink to the surface of a heat-generating electronic device, and immersing the other surfaces of the heat sink in a liquid, which circulates through tunnels in the heat sink material. This innovation was followed by others too numerous to mention by inventor and patent number, including: jacketing the CPU of a computer and placing liquid coolant directly in contact with the CPU jacket, with or without pumps for circulation of the liquid; increasingly complex valves and other electronically controlled redundant cooling components for one or more CPUs or other heat generating electronic components; various designs for the channels and pipes carrying the liquid coolant; closed loop and open loop systems with physical contact between loop housings and varying degrees of fluid exchange between them.
The cooling capacity of the earth's subsurface has long been recognized as a potential energy-saving feature of systems that cool inhabited environments. Because the subsurface maintains essentially a constant temperature at a given depth and the rock and/or artesian mass and volume of the subsurface are vast, heat can be exchanged with either warmer surface fluid, thereby providing cooling, or cooler surface fluid, thereby providing warming. Vignal and Chapuis, in U.S. Pat. No. 3,965,694 (1976) describe a means of exchanging heat with the earth's subsurface via a U-shaped line or pipe buried in a deep hole bored in the earth; their design is directed at systems for warming or cooling above-ground air. Many devices since then have been disclosed that improve on various aspects of air-conditioning designs and provide for more efficient heat transfer between above-ground fluids and subsurface rock or liquid.
The use of subsurface thermal capacity to control the operating temperature of electronic equipment was disclosed by Enlund in U.S. Pat. No. 6,397,933 (2002) for equipment installed in a station and by Kidwell and Fraim in U.S. Pat. No. 7,363,769 (2008) for the cooling of electronic equipment at the base of an electromagnetic signal transmission/reception tower. The subject matter disclosed by Kidwell and Fraim describes a method and apparatus for using coaxial flow heat exchanging structures for regulating the temperature of heat-generating electronics installed in the base housing of an electromagnetic signal transmission/reception tower. The heat transfer is effected using a fluid flow loop from the surface to the underground environment and back to the surface. Chainer, in U.S. Pat. Application No. 2013/0081781 describes a system for data center cooling wherein heat transfer fluid is removed from the indoor volume of the data center and cooled via ambient air and geothermal heat exchange processes.
Attlesey, et al. in U.S. Pat. No. 7,724,517 (2010) disclose a design of a case for a liquid submersion cooled electronic device; the embodiments described therein include a liquid-tight case for enclosing electronic equipment, with at least a portion of one of the walls composed of translucent or transparent material for visibility into the interior of the case. In several subsequent patents, Attlesey describes cooling of electronic equipment by means of a dielectric liquid circulating in and through a fluid-tight container. Tufty et al. disclose a similar approach in U.S. Pat. Application No. 2013/0081790 (April 2013). Campbell, et al. in U.S. Pat. No. 7,961,475 (June 2011) describe an apparatus and method for immersion cooling of one or more electronic subsystems in which cooling fluid passes in and out of one or more containers docked within an electronics rack.
In conclusion, the heat generated by computer and other electronic hardware results in significant cooling costs in environments, such as data centers, where systems are deployed in high density configurations.
Unless specifically stated as such, the preceding is not admitted to be prior art and no statement appearing in this section should be interpreted as a disclaimer of any features or improvements listed.